Background: In Canada, the 2-step approach for the diagnosis of gestational diabetes (GDM) continues to be used, due to uncertain treatment benefit at the lower diagnostic thresholds recommended by the International Association of Diabetes and Pregnancy Study Groups (IADPSG). GDM diagnosed by 2 step criteria is associated with an elevated risk of subsequent diabetes; however, the impact of GDM based on IADPSG criteria on future diabetes risk is unknown.
Aim: To evaluate the risk of future diabetes associated with a GDM diagnosis using the 2 step and IADPSG criteria.
Methods: Using Ontario population-based databases, we evaluated the incidence of diabetes in women with a live birth recorded between April 2011 and March 2014 and available prenatal glucose tolerance test records. Women were categorized according to their prenatal glucose tolerance results as no GDM, GDM based on 2-step criteria, and GDM based on IADPSG criteria (positive by IADPSG, negative by 2 step criteria). They were followed until April 2018 for a diagnosis of diabetes. Risk of diabetes associated with GDM based on each definition was compared to no GDM using a multivariable Cox proportional hazards model.
Results: Of the 104,942 women included in the study, 5,371 (5.1%) had GDM by 2 step criteria and 2,436 (2.3%) had GDM based on IADPSG criteria. There were 821 (0.78%) diabetes cases over 329 771 person-years of follow-up. After adjusting for age, body-mass index, history of GDM, gestational weight gain, birth weight, income, and ethnicity, diabetes risk was significantly higher for both GDM women by 2 step criteria (HR 14.1; 95% CI 11.7-16.9) and for GDM based on IADPSG criteria alone (HR 3.1; 95% CI:2.0-4.7) compared to no GDM.
Conclusion: While the relative risk of diabetes compared to normal glucose tolerance is higher for women diagnosed with GDM using the conventional 2 step criteria, GDM based on IADPSG criteria also confers a significant 3-fold increase in diabetes risk.
B. Balaji: None. S. Read: None. H. Berger: None. D. Feig: Advisory Panel; Self; Novo Nordisk A/S. Speaker’s Bureau; Self; Medtronic. B.R. Shah: None. L. Lipscombe: None.